1. Field of the Invention
The invention relates to an image forming apparatus and, more particularly, to an image forming apparatus such as a monochromatic or full color copying machine or printer using a photosensitive microcapsule.
2. Description of Related Art
Conventionally known is a so-called photosensitive microcapsule formed by encapsulating a core substance in an outer shell. The core substance is composed of an image forming material and a photocuring substance. The image forming material is a dye precursor, dye or pigment. The photocuring substance is sensitive to light having a certain wavelength to change its mechanical strength. The outer shell is formed of resin. Accordingly, the photosensitive microcapsule is cured when exposed to light having a certain wavelength.
Further, an image forming apparatus using such a photosensitive microcapsule is also generally known. The image forming apparatus employs a photosensitive medium formed by coating a plurality of photosensitive microcapsules with a binder on a substrate. The substrate is a plastic film formed of PET (polyethylene terephthalate). In forming an image, the photosensitive medium supporting the photosensitive microcapsules is first exposed to light having image information. As a result, the photosensitive microcapsules on the photosensitive medium are selectively cured to thereby form a chemical latent image according to differences in the mechanical strength between the photosensitive microcapsules on the photosensitive medium. Thereafter, an image receiving medium is superimposed with the photosensitive medium, on which the chemical latent image has been formed, and a pressure is applied to the image receiving medium and the photosensitive medium, thereby rupturing uncured ones of the photosensitive microcapsules to discharge the image forming material from the ruptured microcapsules.
In the case where the image forming material is a dye precursor, a special paper having a developer layer as an absorbing layer is used as the image receiving medium, while in the case where the image forming material is a dye or a pigment, a plain paper or the like is used as the image receiving medium. The image forming material discharged from the microcapsules is absorbed by or deposited on the image receiving medium, thereby forming an image on the image receiving medium.
However, the photosensitive medium to be used in this apparatus employs a plastic film as the substrate as mentioned above. Once the image is formed with use of the photosensitive medium, the substrate of the photosensitive medium is discarded with the spent microcapsules in spite of the fact that the substrate does not directly contribute to the image formation. Accordingly, the operating cost is high in this image forming apparatus.
To cope with this problem, the same applicant as that of the present application has disclosed, in Japanese Patent Application No. 3-124919, an image forming apparatus capable of forming an image by using only powdered photosensitive microcapsules without using a substrate as described above.
In this image forming apparatus, the powdered photosensitive microcapsules are first applied, in a dry condition, to a support member formed as an endless belt or a roller. Then, the coating of the photosensitive microcapsules on the support member is exposed to light having image information. As a result, the photosensitive microcapsules on the support member are selectively cured to thereby form a chemical latent image according to differences in the mechanical strength between the photosensitive microcapsules on the support member. Then, the support member is superposed on an image receiving medium and they are pressed by a pressure roller or other means for the application of pressure. As a result, the uncured photosensitive microcapsules are ruptured and the core substance of the uncured microcapsules is discharged. The core substance thus discharged from the ruptured microcapsules is transferred to the image receiving medium, thereby forming an image on the image receiving medium. Thereafter, a residue, including the cured photosensitive microcapsules and the outer shells of the ruptured microcapsules, left on the support member is removed from the support member by a cleaning blade or similar apparatus. Thus, the support member can be used repeatedly.
However, the above residue also contains some of the core substance. Since the core substance is a liquid material containing an adhesive polymerizable monomer as a primary component, it is difficult to completely remove the residue from the support member by using a cleaning blade or similar apparatus. Accordingly, the support member is imperfectly cleaned as it is repeatedly used so that a clear image cannot be formed on the image receiving medium.